{ "number": 617, "headline": "May 27, 2025 Tuesday Tropical Update", "standfirst": "Tropical Storm Alvin likely to form in Eastern Pacific", "desk": "tropics", "dateline": { "place": "Weather Trader", "state": null, "lat": null, "lon": null, "site_key": null, "site_name": null, "site_url": null, "accent": null }, "edition": "2025-05-27", "published": "2025-05-27T14:38:44.353000Z", "updated": null, "access": "free", "body_html": "
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Tuesday\u2019s Tropical Weather Headlines

  1. Atlantic tropical update: not expecting any development through at least 7-days, but chance for something in the Caribbean or Gulf of Mexico after Day 10 as the Atlantic hurricane season gets underway in June. No chances of a \u201cpre-season\u201d system.

    A Caribbean / Central American gyre circulation in early June is conducive to spinning up tropical storms in the Eastern Pacific & Caribbean/Gulf.

  2. Eastern Pacific tropical update: Global models agreement \u2014 Eastern Pacific to see first storm [Alvin] before in the next 48-72 hours. NHC is up to 90% chance in 48-Hours in the Outlook. Alvin should become a Hurricane over 30\u00b0C SST.

Integrated Vapor Transport | Next 10-days

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A surge of moisture from the Lesser Antilles into the Caribbean reaches the Gulf of Mexico by Day 10. This pattern is conducive for tropical storm development into the second week of June.

Alvin parallels the coast of Mexico and decays prior to making landfall, most likely. The moisture is pulled into the U.S. Southwest to enhance rainfall chances over Southern California and Arizona, including Phoenix into early next week.

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Atlantic Basin

Eastern Atlantic Satellite Image

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Large cloud-free dust haze has moved further in the Eastern Atlantic with a strong Saharan Air Layer (SAL). Tropical waves over Burkina Faso and Sudan are vigorous, and several days from emerging over the Atlantic. The Easterly Wave season is underway but we don\u2019t expect development in the Main Development Region (MDR) of the tropical Atlantic until July.

NASA GEOS-5 Dust | 7-days Forecast

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SAL into Lesser Antilles will make the Gulf in 3-4 days. Then, the next major plume will be right on its heels. The dust inhibits solar radiation from reaching the ocean surface \u2014 net cooling!

Atlantic Ocean Surface Temperatures (SST) and Anomaly

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Actual sea-surface temperatures < 26\u00b0C won\u2019t support tropical storm genesis through normal convective pathways shutting off the MDR for a while. The Gulf and Caribbean are open for business with 28\u00b0C surface water available.

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Anomaly (compared to 1991-2020) is 1-2\u00b0C above normal across the Gulf and into the Southwest Atlantic off the coast of Florida to Bermuda. However, even if it\u2019s warmer than normal, the actual T is still < 26\u00b0C.

Important: actual Sea-Surface Temperatures (SST) help form and intensify tropical storms and hurricanes NOT the anomaly. We need sustained 26\u00b0C SST for typical tropical pathway storm development. You can see the green (under 26\u00b0C) extends still to 10\u00b0N latitude = too chilly for typical MDR development, but that will warm over the next 2-weeks to be viable.

The Caribbean is already (always) warm enough for a major hurricane (28\u00b0C). The Gulf is still chilly across the northern half of the basin.

Tropical Atlantic Satellite Imagery

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Two tropical waves \u2014 one heading through Venezuela = moderate convection, and another approaching the NE coast of South America with some convection.

Tropical Surface Analysis 06Z

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Tropical Waves = 2 but no development in the Atlantic

However, no tropical development expected. But these systems can provide the seedlings for Eastern Pacific hurricanes in 10-14 days from their emergence off African coast.

Long range model outlook

ECMWF 00z | Day 10

Both ECMWF and GFS show a disturbance in the Caribbean or over Yucatan into the Gulf of Mexico by Day 8-10 suggestive of decent chance of a tropical storm. There is some ensemble support. Still quite a ways out over the skillful forecast horizon.

GFS 00z | Day 10

ECMWF Ensembles | 10-Days Active Tropical Storm Tracks

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Day 13

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Day 15

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There are 10/51 (20%) or so that show a strong tropical storm or hurricane in the next 15-days into mid-June. Worth watching!

Eastern Pacific Tropical Update

Invest 90E designated by NHC with 90% chance of tropical storm development in the next 48-hours.

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Upper-level wind shear is not ideal with a cut-off low dipping off Southern California to help steer Invest 90E (Alvin) quickly to the north and then northeast over colder water into Mexico.

Precipitable Water Animation | ICON 06z

My favorite weather parameter shows Alvin over the next 5-days near the coast of Mexico.

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Model Spaghetti Tracks

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SSTs very warm in Eastern Pacific near coast of Mexico > 30\u00b0C

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Note the cooler equatorial waters under 26\u00b0C = green and below normal.

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HWRF Mesoscale Model

Intensity of Alvin?

HWRF is near major hurricane pressure and winds.

HAFS (A and B) are weaker, but still Category 1 hurricane. Makes more sense with upper-level conditions.

ECMWF 00z Ensembles | Eastern Pacific

Day 3.5

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Day 10 \u2014 additional development possible on the heels of Alvin in line with climatology of the Eastern Pacific. June is a rather busy month out there!

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Day 15

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Maps sourced from weathermodels.com designed and innovated by yours truly! Please subscribe there for real-time access to the newest maps, charts from all of the weather models including ECMWF.

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Atlantic tropical update : not expecting any development through at least 7-days, but chance for something in the Caribbean or Gulf of Mexico after Day 10 as the Atlantic hurricane season gets underway in June. No chances of a \u201cpre-season\u201d system.

A Caribbean / Central American gyre circulation in early June is conducive to spinning up tropical storms in the Eastern Pacific & Caribbean/Gulf.

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